AT&T UNIX™PC Unix System V Users Manual - tenox

TAM(3T) (AT&T UNIX PC only ) TAM(3T)
according to which window is obscuring which other windows.
The top window in the sequence is always completely visible.
When a window is selected, it moves to the top, potentially overlaying
windows that were previously visible. For windows with
borders, row and column indicate the upper-left corner of the outside
of the window, while height and width describe the dimensions
of the inside of the window. Of the flags, only NBORDER
applies to remote terminal windows. These flags are defined in
window(7) in sysjwindow.h; note that tam.h calls both
window.h and stdio.h .
The iswind(} call determines if the terminal is local or remote.
The differences in the way TAM provides windows for bit-mapped
terminals versus remote terminals are described below.
For the UNIX PC bit-mapped screen terminal, either the same process
(application) or distinct processes can own simultaneous windows.
The UNIX PC kernel remembers the covered portions of any
window on a pixel basis. Each window is a separate device and
can have its tty modes set independently of the other windows.
Since file descriptors are used to access windows, a child process
can inherit the open windows of its parent. All of the usual UNIX
system calls apply, so an application can set the "close on exec"
bit via fcntl(} to prevent access to particular windows by a child
process.
A process can also set up a child process so that its standard input
and output point to a particular window by the usual techniqueclosing
file descriptors 0 and 1 ( stdin and stdout) and duplicatiTJ.g
the window's file descriptor. Window changed signals are sent to
the process group associated with the particular window. Thus,
by default, a parent process receives signals concerning windows
created by its children. To prevent a parent from receiving these
signals, use the setpgrp(} system call.
In the case when the child process is unaware of windows, the following
parameters should also be fixed: tty modes should be set to
reasonable values and the signal SIGWIND should be ignored
rather than caught. (SIGWIND is ignored by default.)
A window which is owned by a particular application can be
manipulated without the consent of the application. A signal
(SIGWIND) is sent to the process group associated with the window
to report any window changes. If a single process creates
multiple windows, it receives the SIGWIND signal when any of its
windows are changed. To respond appropriately to changes in its
window, an application must catch SIGWIND (the default is to
ignore SIGWIND) and issue a wgetstat() (described below) to
determine which windows changed and in what ways.
If an application changes characteristics of its own window, no signal
is sent to the application. In fact, when any process in the
process group associated with the window changes the window
characteristics, no signal is sent. Some care should be taken when
an application changes its own window, since this might defeat the
wishes of the operator. For example, if a process makes its
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